SODIUM THIOSULPHATE (Hyposulphite)
Colourless crystals, soluble in water to a neutral solution. It may con-
tain sulphides, sulphates, sulphites, carbonates and chlorides.
1. Sulphides.With lead acetate the solution gives an immediate
black coloration or precipitate in presence of sulphide;.
2. Sulphates, Sulphites, Carbonates............A solution of i grain in
30 c.c. of water should not be rendered turbid by barium chloride or give
a red coloration with phenolphthalein (sodium carbonate}.
3. Chlorides.The I : 10 solution is boiled with excess of nitric acid,
filtered and tested with silver nitrate.
4. Quantitative Determination.20 grams are dissolved to I litre
and 20 c.c. of the solution (--- ov.|. gram of substance) titrated with
N/io-iodine in presence of starch paste: i c.c. N/io-iodinc = -0-0248 gram
NaaWO, + 211,0 : = 330
Colourless crystals or white or yellowish powder soluble in about 4 parts
of cold water, and often containing excess of alkali. Its value* depends essen-
tially on the content of tungstie acid, which may be determined as follows :
Determination of the Tungslic Acid.......1-2 grams are dissolved in
a little water and any excess of alkali neutralised with nitric acid in presence
of phenolpli.tha.lein, cone, niereurous nitrate solution being then added until
no further formation of precipitate takes place. After thorough shaking
and heating to cause the mercuric tungstate to settle well, the liquid is
filtered and the precipitate washed with dilute mercurous nitrate solution,
dried at loo", ignited (under a hood on account of the mercury vapour
evolved) and weighed as tungstic. anhydride : i part: W().t iv|,2-24 parts
of NaaW(), ~h 211,0.
SnCl4 ; 2ui; SnC'U + 5'lIgO - 351,
This is sold as: Anhydrous stannic- chloride,, heavy, colourless liquid
emitting dense white fumes in the, air, 1) 2-26, b.pt, 115" ; Liquid stannic
chloride, colourless or yellowish aqueous solution of the anhydrous salt,
50-60" Bauni6 ; Solid alannic chloHdc (SnU^f 5'liaO) in white or yellowish,
hygroscopic, crystalline masses.
The commonest impurities consist of free chlorine, nitric and sulphuric
acids, stannous chloride, stannic oxide-, ammonium, lead, iron and alkali
salts (especially NaCl).
1 'See also Sodium Bisulphite.rths, the